/// <summary>
        /// TextProperty property changed handler.
        /// </summary>
        /// <param name="d">AutoCompleteBox that changed its Text.</param>
        /// <param name="e">Event arguments.</param>
        private static void OnTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            HighlightedTextBlock source = d as HighlightedTextBlock;

            source.ApplyText(e.NewValue as string);
        }
        /// <summary>
        /// HighlightBrushProperty property changed handler.
        /// </summary>
        /// <param name="d">HighlightingTextBlock that changed its HighlightBrush.</param>
        /// <param name="e">Event arguments.</param>
        private static void OnHighlightBrushPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            HighlightedTextBlock source = d as HighlightedTextBlock;

            source.ApplyHighlighting();
        }